After reading about the American missionary killed on North Sentinel Island, I realized I'm not sure how to answer the following question. One of the reasons anthropologists advise avoiding the remote island is to spare the Sentinelese tribe from our germs because they don't have immunity. The same thing happened to native South American tribes when the Portuguese and Spanish arrived (over 90% of the population was decimated from disease). My question then is why is that the native tribes were more susceptible to European diseases and not the other way around? Why weren't the Spanish and Portuguese decimated by native diseases?
There are apparently several reasons. I found an article (http://www.todayifoundout.com/index.php/2014/03/native-americans-didnt-wipe-europeans-diseases/) that basically calls out three specific reasons:
- Europeans had lived with and near domesticated animals for quite a while, and this helped boost their immune systems. Native Americans, for the most part, were hunter-gatherers who did not keep livestock.
- Europeans lived close together, and the interaction (and exchange of germs) that this caused helped to boost their immune systems.
- Europeans traveled a lot and interacted with citizens of other areas to a larger degree, and this helped boost their immune systems.
Recurring theme? Several factors combined to help boost the immune systems of Europeans as compared to Native American tribes.
However, if you read the article (recommended) you will find that it was a two-way street, at least to a degree. For example, one of the best-known diseases acquired in the New World and brought back to Europe was syphillis.